Skin care compositions containing retinoids have become the focus of great interest in recent years. Retinoic acid, also known as Vitamin A acid or tretinoin, is well-known for the treatment of such skin conditions as acne and products containing retinoic acid are commercially available in various forms from the Dermatological Division of Ortho Pharmaceutical corporation.
More recently, however, wider use of retinoids has been suggested for treatments other than acne such as, for example, the treatment of skin against photoaging and sun damage. Many individuals who have had a good deal of sun exposure in childhood will show the following gross cutaneous alterations in later adult life: wrinkling, leatheriness, yellowing, looseness, roughness, dryness, mottling (hyperpigmentation) and various premalignant growths (often subclinical). These changes are most prominent in light-skinned person who burn easily and tan poorly. These cumulative effects of sunlight are often referred to as "photoaging". Although the anatomical degradation of the skin is most advanced in the elderly, the destructive effects of excessive sun exposure are already evident by the second decade. Serious microscopic alterations of the epidermis and dermis occur decades before these become clinically visible. Wrinkling, yellowing, leatheriness and loss of elasticity are very late changes.
The problem of skin aging is addressed in U.S. Pat. No. 4,603,146 wherein Vitamin A acid in an emollient vehicle is suggested as a treatment. Further, in U.S. Pat. No. 4,877,805, it is suggested that a number of retinoids are useful for restoring and reversing sun damage of human skin.
When considering the use of retinoids in skin care products, it is believed that certain retinoids such as, for example, retinol (Vitamin A alcohol), would be preferred over retinoic acid. This is because retinol is an endogenous compound naturally occurring in the human body and essential for good growth, differentiation of epithelial tissues and reproduction. Retinol is also preferred because it has a much larger safety margin than other retinoids such as retinoic acid. Accordingly, attention has turned toward formulating skin care compositions which contain retinol. Such compositions have been proposed such as those disclosed in a pending patent application, U.S. Ser. No. 719,264, filed on Jun. 27, 1991 by Clum et al. and commonly assigned to the assignee of this application; the disclosure of which is hereby incorporated by reference.
The benefits from the use of retinol as set out above notwithstanding, it has been noted that skin care compositions containing retinol to some degree exhibit undesirable skin irritation as manifested by flaking, erythema and dermal edema.
Accordingly, there is a need for a composition comprising retinol which manifests less retinol induced irritation.